On Sun, Feb 9, 2014 at 7:17 PM, David Roberson <[email protected]> wrote:
> OK. Energy is proportional to velocity squared. If you double the > velocity, you have four times as much energy as in the first case. Also > the direction of the motion is not important. For example, a ball moving > to the right has a certain amount of energy and a second one moving to the > left with the same mass and velocity will have the same amount as well. > Energy adds, so you have two times the amount contained within one. > > Momentum is proportional to velocity directly. The direction of the > movement is important since momentum is a vector quantity, unlike energy. > The two ball case above results in a net momentum for the system of zero. > The two vectors are equal and point in opposite directions so they cancel. > > Energy and momentum require different rules of behavior and can not be > interchanged. > > Dave That is a good summary. As a corollary to the last statement, I would add that momentum cannot be turned into heat since heat is considered a form of energy. Harry
